Working Principle of Lithium-ion Batteries

Lithium-ion batteries use carbon as the anode and lithium-containing compounds as the cathode. There is no metallic lithium, only lithium ions. The term "lithium battery" commonly refers to batteries that use lithium-ion intercalation compounds as the cathode material.

The charge and discharge process of lithium-ion batteries involves lithium-ion insertion and extraction. During this process, lithium ions and equivalent electrons move in tandem: insertion is typically used to describe the cathode process and intercalation or insertion for the anode. During charge and discharge, lithium ions shuttle between the cathode and anode, often described as a "rocking-chair" mechanism.

When charging, lithium ions are released from the cathode and move through the electrolyte to the anode. The carbon anode structure has many micropores where lithium ions intercalate. The more lithium ions intercalated, the higher the charge capacity. During discharge (the battery in use), intercalated lithium ions leave the carbon structure and move back to the cathode; more lithium ions correspond to higher discharge capacity.

Recommended charge current is typically between 0.2C and 1C. Higher current charges faster but produces more heat. Electrochemical reactions in the battery require time, so excessively high charging current may reduce effective capacity.

Usage (discharge) precautions:

Normal use involves discharge. Pay attention to the following when discharging lithium batteries:

First: avoid excessively large discharge currents. Large currents cause internal heating and may cause permanent damage.

As shown in the figure, higher discharge currents lead to reduced discharge capacity and faster voltage drop.

Second: avoid over-discharge. Stored chemical energy is reversible, and excessive discharge can cause irreversible reactions. If cell voltage falls below about 2.7V, the battery may be damaged. Many portable batteries include protection circuits that stop discharge before reaching damaging voltages.